SHED-FORMING DEVICE

Abstract

The disclosure concerns a shed-forming device including a jacquard device in which the heddles, are connected to a pull-back element, for exerting a downward force on the heddle, wherein for each heddle, a yarn tensioning element is provided to change the yarn tension in at least one associated warp thread, and where a control or steering unit is provided for steering or controlling the yarn tension in at least one associated warp thread, separately for each heddle, in order to bring the total downward force on the heddle to a specific value or vary this according to a specific profile.

Claims

1. Shed-forming device comprising a jacquard device with a number of heddles, for positioning at least one associated warp thread, wherein each heddle is connected to a pull-back element, for exerting a downward force on the heddle, wherein the shed-forming device comprises, per heddle, a yarn tensioning element which is provided to change the yarn tension in at least one associated warp thread, and that the shed-forming device comprises a control or steering unit which is provided, in cooperation with the respective yarn tensioning elements, for steering or controlling the yarn tension in at least one associated warp thread, separately for each heddle, such that the total downward force on the heddle, is brought to a specific value or varies according to a specific profile.

2. Shed-forming device according to claim 1, wherein each yarn tensioning element comprises a roller which is driven by a motor and which is in contact with at least one warp thread, and which is intended to rotate in the one or the other direction of rotation in order to move said warp thread in a direction opposite the feed direction of the warp threads, or to move the warp thread or to move with the movement thereof or to facilitate the movement thereof in a direction which is the same as the feed direction of the warp threads, in order to increase or decrease respectively the yarn tension in said warp thread.

3. Shed-forming device according to claim 1, wherein that parameters of the jacquard device or of a weaving machine cooperating with the jacquard device, or data or parameters connected with the weaving pattern, are made available to the control or steering unit in order to be taken into account in determining the target value for the total downward force.

4. Shed-forming device according to claim 1, wherein it comprises a storage unit in which two or more reference yarn tension profiles and/or two or more reference series of at least one reference value for the yarn tension are stored, and that the control or steering unit is provided to select a reference profile or reference series from this collection in order to use these as target value(s) or a succession of target values for steering or control.

5. Shed-forming device according to claim 1, wherein the pull-back elements are springs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In this description, reference signs are used to refer to the attached figures, in which:

[0024] FIG. 1 is a diagrammatic side view of a structure of a weaving machine and a bobbin creel with associated yarn tensioning device;

[0025] FIG. 2 is a graph showing the following for a pile-forming pile warp thread in a number of successive weft insertion cycles during weaving, according to the prior art: [0026] the development of the position of the heddle eye (in mm), [0027] the development of the upward or downward component of the force (in N) which is exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread, [0028] the development of the downward spring force exerted by the pull-back spring on the heddle of the pile warp thread (in N), and [0029] the development of the sum of the downward spring force (in N) on the heddle and the upward or downward component of the force (in N) which is exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread.

[0030] FIG. 3 is a graph showing the following for a pile-forming pile warp thread in a number of successive weft insertion cycles during weaving with a controlled or steered yarn tension according to the disclosure: [0031] the development of the position of the heddle eye (in mm), [0032] the development of the upward or downward component of the force (in

[0033] N) which is exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread, [0034] the development of the downward spring force exerted by the pull-back spring on the heddle of the pile warp thread (in N), [0035] the development of the sum of the downward spring force (in N) on the heddle and the upward or downward component of the force (in N) which is exerted on the heddle as a result of the yarn tension in the pile-forming pile warp thread, and [0036] the mean of said sum of forces.

DETAILED DESCRIPTION

[0037] In a particular installation, a weaving machine (1) in cooperation with a jacquard device (2) is installed next to a bobbin creel (3), and a beam stand (4) with four rollers (40)-(43) each containing a yarn store is arranged in the space between the weaving machine (1) and the bobbin creel (3).

[0038] A yarn tensioning device (6) is installed in the space between the bobbin creel (3) and the weaving machine (1), and consists of a yarn tensioning module (20) which extends in the horizontal direction parallel to a vertical plane containing the front sides (30a) of the plurality of mutually adjacent creel units (30). The yarn tensioning module (20) consists of two panel-like carriers (21), (22) with a flat outer surface, which run symmetrically relative to a horizontal plane towards each other in the direction of the weaving machine (1), wherein they converge and join together at an angle. The yarn tensioning module (20) has a V-shaped profile viewed in a vertical cross-section. Each carrier (21), (22) carries a large number of rows of yarn tensioning elements (8) placed closely adjacent to each other. For reasons of clarity, only three yarn tensioning elements (8) are shown for each carrier (21), (22). For each warp thread which is guided from a respective bobbin in the bobbin creel (3) to the weaving machine (1), a guide tube (10) is provided for guiding the warp thread without tension to a respective yarn tensioning element (8).

[0039] The warp threads are moved further from the yarn tensioning elements (8) to a grid (100) with the same width as the yarn tensioning module (20) but with a smaller height. From the grid (100), the warp threads (11), (12) run to the weaving machine (1) where they pass through the heddle eye of a respective heddle (16), (17), shown symbolically by a vertical line with a circular widening which depicts the heddle eye. A respective pull-back spring (18), (19) exerts a downward force on each heddle (16), (17).

[0040] According to the prior art, the warp threads are supplied in stretched state from the bobbin creel (3) to a first grid (X). FIG. 1 shows the situation of the prior art with the straight line (S1) which runs from the top row of bobbins in the bobbin creel (3) firstly through the grid (X) of an existing installation and then on to the grid (100), and the straight line (S2) which runs from the bottom row of bobbins in the bobbin creel (3) via the grid (X) of an existing installation and then on to the grid (100). For the sake of clarity, the grid (X) does not form part of the installation according to this disclosure and is merely added to the figure in order, by comparison with the prior art, to be able to present an effect of the disclosure.

[0041] The lines (S1), (S2) show the size of the angles (relative to a horizontal plane) at which the warp yarns are brought to the grid (X) and then on to the grid (100) according to the prior art, and consequently the angle which the supplied warp threads then take.

[0042] During weaving, the heddles (16), (17) are moved up and down in order to position the warp threads (11), (12) correctly according to the predefined weaving pattern. The pull-back springs (18), (19) in their lowest position provide the necessary downward force for allowing the shed formation to proceed correctly, but must also overcome the upwardly directed force which is a consequence of the yarn tension.

[0043] If the heddle is moved to a higher position for shed formation, the downward spring force increases proportionally with the upward movement of the heddle in order finally to reach a value which is much greater than necessary.

[0044] On FIG. 2, for a number of successive weft insertion cycles (the state of the main shaft of the weaving machine is shown on the horizontal axis in degrees), graph line G1 shows the development of the downward force which the springs (18), (19) exert on the heddle (16), (17) (on the left vertical axis, in N) of a pile-forming pile warp thread; and graph line G2 shows the development of the alternating upward and downward component of the force (in N) which is exerted on the heddle (16), (17) as a result of the yarn tension in the pile-forming pile warp thread. The latter force is referred to in brief below as the “yarn tensioning force”.

[0045] For the sake of clarity, where a force (spring force or yarn tensioning force) is marked as negative in FIGS. 2 and 3, this means that the force is pulling the heddle upward. This is clear for example because the yarn tensioning force is negative in the graph regions where the heddle is in its lowest position. It is evident that the force exerted by the yarn tension on the heddle then has an upwardly directed component which pulls the heddle upward.

[0046] Graph line G4 shows the position of the heddle eye (in mm on the vertical axis on the right-hand side).

[0047] Graph line G3 shows the development of the sum of the spring force and the yarn tensioning force. Here we see two high peaks (P1), (P2) of this total force. The graph line G3 shows the forces to which the different machine components are subjected. It should be noted that the graphs in FIGS. 2 and 3 show the forces which are the result of movements of a single pile warp thread, whereas on a typical face-to-face weaving machine for example, 32,000 pile warp threads or more may be present.

[0048] FIG. 3 shows the development of the spring force and the yarn tensioning force on the heddle of a pile-forming pile warp thread when the yarn tension is controlled or steered so as to achieve lower peak values and a lower mean of the sum of the spring force and yarn tensioning force.

[0049] Because of this steering or control, also a spring may be used with a lower spring constant and a lower spring pretension force (0.15 N lower)—this is the downwardly directed spring force when the heddle is in its lowest position. The pretension force may be lower because, thanks to the steering or control of the yarn tension, less upward yarn tensioning force is exerted by the pile warp thread.

[0050] In FIG. 3, the same indications (G1), (G2), (G3) and (G4) are used for the graph lines as on FIG. 2, with the same meanings: namely the development of the downward spring force (G1), the development of the yarn tensioning force (G2), the development of the sum of the spring force and the yarn tensioning force (G3), and the position of the heddle (G4). The left vertical axis gives the values of the forces (in N), and the right vertical axis gives the values of the positions of the heddle (in mm). The horizontal axis gives the state of the main shaft of the weaving machine in degrees.

[0051] Graph line (G5)—the dotted line—gives the value of the mean of said sum of the spring force and yarn tensioning force.

[0052] It is clear from graph line (G3) that for the total force on the heddle, the high peaks have disappeared (compare with FIG. 2, peaks P1 and P2). In addition, the mean value of this total force is lower. In the design without a steering or control system (FIG. 2), the calculated mean of this total force is 2.91 N, while in the design with control system, this total force is 2.72 N (graph line G5 on FIG. 3).

[0053] These effects mean a lower load on the machine, wherein again it must not be forgotten that the values from the graphs show the forces which are the result of the movements of a single pile warp thread, whereas on a typical face-to-face weaving machine for example, 32,000 pile warp threads or more may be present.

[0054] The advantageous aspects of this disclosure are not restricted to pile warp threads but also apply to warp threads of another type which are positioned by the jacquard device, or to single-face weaving machines.